Scientists call for intensified slaughter to control disease

Published: Friday, April 13, 2001

Associated Press

WASHINGTON {AP} An expanded program of preventative livestock slaughter may be the most effective way to halt the spread of foot-and-mouth disease among England's farm animals, say British researchers.

Scientists at the Imperial College School of Medicine in London have called for a policy of "ring culling," a system in which all livestock within about a mile of an infected animal are killed.

"Extensive culling is sadly the only option for controlling the current British epidemic and it is essential that the control measures now in place are maintained during the long decay phase of the epidemic to ensure eradication," the authors say in a study appearing Friday in the journal Science.

The authors are Neil Ferguson, Christl Donnelly and Roy Anderson, all researchers in the department of infectious disease epidemiology at the St. Mary's campus of the Imperial College School of Medicine.

An outbreak of foot-and-mouth disease hit Britain seven weeks ago, starting with a pig herd in Northumberland. It since has affected cows and sheep and has spread to parts of France, Ireland and the Netherlands.

Humans cannot catch the disease from the meat of infected animals, but products from animals with foot-and-mouth are not marketed due to the extreme risk of spreading the disease.

Foot-and-mouth is a virus that can be spread through indirect contact. The virus can be carried by the wind or spread through contact with the saliva, milk or dung of affected animals. New infections can arise from the virus from contaminated clothing of people working with infected animals. Dogs, cats, poultry and wildlife can all spread the disease through contact with the virus. Even trucks carrying infected animals can spread the disease.

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Officials say the only effective treatment for foot-and-mouth epidemics is to isolate and destroy infected herds.

British agricultural officials have been attempting to control the disease by forbidding transportation of animals within England, canceling livestock shows and exhibitions, and by slaughtering all animals in herds where the disease appears, along with animals at adjacent farms.

But the three researchers say this may not be enough.

Ferguson, Donnelly and Anderson said a computer study shows that the best approach will be to slaughter all infected animals within 24 hours, followed within 48 hours by the destruction of all potentially affected animals within about a mile of the infection focal point.

A type of ring culling already is being practiced in the worst-hit area, Cumbria in northwestern England, where all animals within 2 miles of an infection site are being slaughter.

The researchers estimate that this rapid, pre-emptive slaughter of livestock would limit the disease to about 16 percent of the farms in Britain, although the rate could soar to 53 percent in some areas.

Continuing the current policy, the researchers say, would result in about 30 percent of all farms in the United Kingdom being affected by the disease.

At least 631,000 animals already have been killed in Britain and some experts believe the epidemic is approaching its peak. The researchers said the disease control measures need to be maintained for several months after the final identified case to ensure that the epidemic is ended.

A foot-and-mouth disease epidemic last struck Britain in 1967 and resulted in the slaughter of 440,000 animals.